JPS6348822B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high temperature resistor composition and a resistor for ceramic heaters. Conventional resistors for ceramic heaters include SiC or BaTiO ₃ -based PTC thermistors, but the former can be used up to high temperatures around 1500℃, but the drawback is that the temperature characteristics of the resistance are very large, and the latter can be used at very high temperatures.
It can only be used up to around 300℃. The present invention aims to provide a heater resistor with a small rate of change in resistance at high temperatures and a resistor composition with ohmic characteristics that can be used at high temperatures. _{2O3 ,}
It is characterized by a composition consisting of 0.2 to 20 mol% of an oxide consisting of at least one of Y ₂ O ₃ , Nd ₂ O ₃ and Gd ₂ O ₃ , and a resistor obtained by firing the same. , a ceramic heater and a high-temperature ohmic resistor with a small temperature change rate of resistance up to a high temperature of 800°C can be obtained. The specific resistance of this ceramic can be freely obtained within the range of 0.1 to 100 Ω-cm. It is also extremely resistant to heat shock, which is an important characteristic for a heater.For example, a rod-shaped ceramic heater with a length of 200 mm, a width of 20 mm, and a thickness of 2 mm is used, and a voltage is applied to it to heat it to a temperature of 800°C. Even when 100ml of water is suddenly poured on top of the heater, it does not break and the temperature quickly returns to 800℃. The shape of the heater can be freely controlled when molding the raw material powder, and it can also be extruded or printed on a substrate such as alumina. The heater resistor and high-temperature ohmic resistor according to the present invention have a small temperature change rate of resistance, and are approximately
Since the resistance is constant up to 1000℃ and increases at higher temperatures, it has the excellent advantage of preventing overcurrent, and is a completely new resistor for oxide semiconductor ceramic heaters and high-temperature ohmic resistors that have never been seen before. It is the body. This will be explained below by giving examples. ZnO, La ₂ O ₃ , Y ₂ O ₃ , Nd ₂ O ₃ , and Gd ₂ O ₃ were mixed as shown in Table 1, and the molding pressure was 1000 Kg/cm ² and the length was 250 mm, the width was 25 mm, and the thickness was 2.5 mm. Molded to 1150~1450
Each was held at a temperature in the range of °C for 1 hour.
The shape of the fired body was 200 mm long, 20 mm wide, and 2 mm thick, and ohmic silver electrodes were provided on both end faces.
The specific resistance and temperature change rate of resistance of this product were measured, and the results are shown in Tables 1 and 2. Figure 1 shows the resistance-temperature characteristics of a typical element. As is clear from Table 1, 99.8 to 80 mol% of ZnO and 0.2 to 20% of one or more oxides selected from La ₂ O ₃ , Y ₂ O ₃ , Nd ₂ O ₃ and Gd ₂ O ₃ % is a semiconductor ceramic heater with low resistance and a temperature change rate of resistance within 30% over a wide temperature range. It was confirmed that equivalent characteristics can be obtained even if two or more types of elements are used within this composition ratio range. When the proportion of the oxide of the rare earth element is less than 0.2 mol% or greater than 20 mol%, the rate of change in resistance is large. From Table 2, the firing of the composition is from 1200 to
When carried out at a temperature within the range of 1400°C, the resistance change rate of the obtained heater resistor is within 30%, and at temperatures outside this range it becomes very large.

【table】

【table】

[Table] The specific resistance is the value when the element temperature is 20°C, and the rate of change was calculated using the following formula. R _x −R ₂₀ /R ₂₀ ×100 (%) R ₂₀ is the resistance value when the element temperature is 20℃,
R _x is based on the resistance when the element temperature is 20℃,
This is the maximum value of resistance within the temperature range of the element from 0 to 800°C. The current-voltage characteristics of the device of the present invention were measured at temperatures from room temperature to about 1000° C., and all of the results showed ohmic characteristics. As described above, according to the present invention, it is possible to obtain a ceramic heater resistor and a high-temperature ohmic resistor that exhibit little change in resistance value under high temperatures.

[Brief explanation of the drawing]

The figure is a characteristic diagram for explaining the resistor composition for ceramic heaters and the resistor composition for high temperature use of the present invention.

Claims (1)

[Claims] 1 99.8 to 80 mol% of ZnO and La ₂ O ₃ , Y ₂ O ₃ , Nd ₂ O ₃
and one or more oxides selected from Gd ₂ O ₃
A high temperature resistor composition comprising 0.2 to 20 mol%. 2 ZnO99.8-80 mol% and La ₂ O ₃ , Y ₂ O ₃ , Nd ₂ O ₃
and one or more oxides selected from Gd ₂ O ₃
A resistor for a ceramic heater, characterized in that it is made by firing a composition consisting of 0.2 to 20 mol%.